Simulation of the vertical ground reaction force on sport surfaces during landing

Calcul de la force de réaction du sol lors de la réception d'un saut vertical de 0,45 m, en utilisant deux modèles : le premier pour l'athlète (4 segments) et l'autre pour le sol sportif élastique (5 segments). La simulation a porté sur 48 sols élastiques différents

VERTICAL SURFACE REACTION FORCES DURING LANDING MOVEMENTS ON HARD AND VIBRATING GYMNASIUM SURFACES

Introduction: Usually forces acting on the human body during sports movements are investigated with the help of a force platform. The force platform is placed on a rigid, level surface, although many sports disciplines are performed on a vibrating surface in a gymnasium. The purpose of the present study was to compare the parameters of the vertical surface reaction force during landing after a jump shot in handball on a hard surface and on a vibrating surface in a gymnasium. Methods: Eight experienced handball players were involved in this study. Each of them performed about 15 trials on both a hard and a vibrating surface in a gymnasium. Surface reaction force was measured with a Kistler force platform. Four parameters of the vertical surface reaction force measured on the two different surfaces were statistically compared using two-tailed unpaired t-tests: passive and active peaks, average and maximum loading rate. Results: On the hard surface there is a passive peak of 4.6-8.3 bw (body weight), followed by an active peak of 1.4-3.0 bw. The values of the average loading rate vary from 100-338 bw/s, the maximum loading from 542-978 bw/s. On the vibrating surface, the passive peak varies between 3.3-6.8 bw. In contrast to the hard surface, the passive peak is followed by more than one active peak. There are 3-4 further local maximums, and the loading rate to these local maximums (up to 100 bw/s) reaches values of the loading rate to the passive peak during jogging. The maximum active peaks range from 1.5-3.3 bw. The average loading rate varies respectively from 94-251 bw/s, and the maximum loading rate from 245-860 bw/s. For all subjects but one the passive peak on the vibrating surface was significantly lower compared to the hard surface. Also, for all subjects the average and maximum loading rate to the passive peak are lower on the vibrating surface. Most of these differences are significant. For all subjects the active maximum is - usually significantly - higher on the vibrating surface. Conclusions: The study shows that under load aspects the vibrating surface produces lower passive peaks, average and maximum loading rates during landing movements in sports but higher and more active maximums. For the classification of the investigated surfaces, a load function with, e.g., active and passive peaks, average and maximum loading rates should be developed as independent variables. A further aim is the development of a transfer function to determine the influence of the force platform

Comparison of six different marker sets to analyze knee kinematics and kinetics during landings

In motion analysis marker sets or protocols are mostly developed for gait analysis and it has been shown that the marker set used affects the results of gait analysis. These marker sets are also used for the analysis of high dynamic sports movements. Single-leg landings are a common tool to investigate functional knee stability and further to predict injury risks where frontal plane motion and loading seem to play an important role. Until now, it is unknown how the marker sets affect the motion analysis results of such high dynamic movements. Therefore, the aim of the study was to compare six different marker sets. Three-dimensional motion and force data of single-leg landings in 12 healthy subjects were collected. Six different marker sets consisting of up to 26 markers and two clusters were simultaneously attached to the subjects’ lower limb and pelvis. The results show that particularly, the knee joint angles in the frontal and transverse plane showed the greatest differences between marker sets with in part contrary joint angle directions and great differences in angle magnitude. In addition, the amount of joint load was dependent on the marker set used for analysis. These results show that one must be careful when interpreting and comparing data of the frontal or transverse plane during high dynamic movements